package com.clark.io;

import java.io.IOException;
import java.io.InputStream;

/**
 * Proxy stream that closes and discards the underlying stream as soon as the
 * end of input has been reached or when the stream is explicitly closed. Not
 * even a reference to the underlying stream is kept after it has been closed,
 * so any allocated in-memory buffers can be freed even if the client
 * application still keeps a reference to the proxy stream.
 * <p>
 * This class is typically used to release any resources related to an open
 * stream as soon as possible even if the client application (by not explicitly
 * closing the stream when no longer needed) or the underlying stream (by not
 * releasing resources once the last byte has been read) do not do that.
 * 
 * @version $Id: AutoCloseInputStream.java 1003647 2010-10-01 20:53:59Z niallp $
 * @since Commons IO 1.4
 */
public class AutoCloseInputStream extends ProxyInputStream {

    /**
     * Creates an automatically closing proxy for the given input stream.
     * 
     * @param in
     *            underlying input stream
     */
    public AutoCloseInputStream(InputStream in) {
        super(in);
    }

    /**
     * Closes the underlying input stream and replaces the reference to it with
     * a {@link ClosedInputStream} instance.
     * <p>
     * This method is automatically called by the read methods when the end of
     * input has been reached.
     * <p>
     * Note that it is safe to call this method any number of times. The
     * original underlying input stream is closed and discarded only once when
     * this method is first called.
     * 
     * @throws IOException
     *             if the underlying input stream can not be closed
     */
    @Override
    public void close() throws IOException {
        in.close();
        in = new ClosedInputStream();
    }

    /**
     * Automatically closes the stream if the end of stream was reached.
     * 
     * @param n
     *            number of bytes read, or -1 if no more bytes are available
     * @throws IOException
     *             if the stream could not be closed
     * @since Commons IO 2.0
     */
    @Override
    protected void afterRead(int n) throws IOException {
        if (n == -1) {
            close();
        }
    }

    /**
     * Ensures that the stream is closed before it gets garbage-collected. As
     * mentioned in {@link #close()}, this is a no-op if the stream has already
     * been closed.
     * 
     * @throws Throwable
     *             if an error occurs
     */
    @Override
    protected void finalize() throws Throwable {
        close();
        super.finalize();
    }

}
